Classification of spam

Spam is not one single problem. There are different kinds of spam, and each of them should be attacked in a different way. Here are the three largest divisions:

1. Commercial spam - Today, many businesses have flourished thanks to Internet, and the only place they exist in is the cyberspace. As any business, they want to get as much public into their ``store'' as possible. It was natural for them to start collecting E-Mail addresses and sending information about their products. Slowly, they started collecting more and more addresses and building up huge E-Mail directories.
2. Chain letters, jokes, virus warnings and other hoaxes are another factor originating heavy loads of spam, sometimes called benign spam. The originators are the regular users: Someone finds something funny, interesting or something he feels as a threat (such as a new virus), and sends it to fifteen people. Each one of them forwards it to fifteen people, and they do the same. By the way, they usually send not only the original message, but append it with the address of every user that has so far received the mail, making the mail larger and larger, and unwillingly, revealing the addresses to possible commercial spammers.
3. Mail bombs - The widespread use of the Microsoft Windows operating system, together with their Office and Outlook programs, have contributed to create a new type of virus: a mail bomb. This is due to the programming language embedded in their Office applications, allowing macros --small programs embedded in a document-- to be made part of otherwise text-only objects, such as a letter or a worksheet. Of course, macros can be any kind of code, including a malicious, self-replicating code: a virus. Macro viruses became widespread since 1996, soon after Microsoft began shipping their macro-enabled products. It was, however, not until April 1999 that self-replicating E-Mail macro viruses appeared, the first one being called Melissa. Since then, this has become the favorite type of viruses written by even the most novice programmers -- and, thanks to the addressbook capabilities of the popular mail user agent Microsoft Outlook, it has very quickly become one of the most widespread kinds of virus, because it automatically jumps to the mailboxes of all persons in the user's addressbook.